IgG responses to ESAT-6/CFP-10. IgG antibody titers against Mtb-specific antigens ESAT-6/CFP-10 (4µg/ml). Titration curves of serum antibody responses against a fusion protein of ESAT-6 and CFP-10 (Lionex) in 19 HIV-1-infected persistently TB, tuberculin and IGRA negative (HITTIN). Optical density (OD 415mm) values from antigen-uncoated wells at each dilution were subtracted from serum OD values at that dilution. A positive response was determined by OD values above background, and absent binding curves are demonstrated in red. Controls include 6 individuals with previous TB from Arm 2, and HIV-1-infected controls with active TB with median and interquartile ranges shown. Out of 15 HITTIN tested, 13 demonstrated decreased OD on dilution (68·4%), whereas only 1/6 (16·7%) of Arm 2 participants did (16·7%), and 11/12 (91·7%) controls with active TB. There is no statistically significant difference between IgG+ antibodies in HITTIN compared to the previous TB (Arm 2) group (p=0·18, Kruskal-Wallis test with Dunn's post test correction for multiple comparisons) and active TB group (p=0·06, Kruskal-Wallis test with Dunn's post test correction for multiple comparisons).